Thames & Kosmos Kids First: Crystals, Rocks & Minerals handleiding

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Handleiding

WHAT IS DENSITY?

You must have noticed by

now that even though the ore samples

are about the same size as the other

minerals, they are much heavier.

Density, or the weight of a substance

of a certain size, is an important

distinguishing feature of minerals.

Water has a density of one, as one

cubic centimeter of water

(corresponding to a cube  cm in

length along each edge) weighs

exactly one gram. Your minerals, on

the other hand, have higher densities

than that. Pure iron, has a density of

.. Lead is , and gold is .

Did you

know …

… THAT MINERALS DIFFER

SIGNIFICANTLY IN HARDNESS?

Over  years ago, the mineralogist

Friedrich Mohs developed a hardness scale

using  minerals with different degrees of

hardness, extending from soft talc to the

super-hard diamond. Mineralogists use

the Mohs scale to this day whenever they

investigate the hardness of minerals with

the scratch test. Still, the Mohs scale is not

all that reliable: Hardness grades , , and

 are hardly different from one another,

and levels  and  show drastic jumps

in hardness. With a

hardness level of

, a diamond is

actually about

, times harder

than quartz.

Hardness

Mineral

Tool

Talc

Can be scraped with

fingernail

Gypsum

Can be scratched

with fingernail

Calcite

Can be scratched

with a copper coin

Fluorite

Can be easily

scratched with a

knife

Apatite

Can be scratched

with a knife

Feldspar

Can be scratched

with a steel file

Quartz

Topaz

Corundum

Diamond

Scratches window

glass, creates sparks

when struck with

steel

The largest rough diamond ever

found was from South Africa and

weighed  kg.

CHECK IT OUT

Minerals in the Research Lab

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